PolymersBy: Si Man Lam

Date: June 7, 2005

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What is a Polymer?

• Polymers are commonly known as plastics• Long chain of carbon molecules with repeating

units joined by covalent bonds• Each repeating unit known as a monomer• Polymer is Greek for “many parts”• Imagine a bowl spaghetti – that is how the

molecular arrangement of polymers looks

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Two Groups of Polymers

• Thermoplastic– Soften with heat and harden with cooling– Examples: HDPE, LDPE, PET

• Thermosets– Cured or Hardened with heating– Examples: Bakelite, Epoxy, Polyurethane

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Natural Polymers

• Existed since the beginning of time• Examples include shellac, turtle shells and horns,

latex, silk• Chemically modified natural polymers include

rubber and gun cotton

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World War II: Revenge of the Synth

• Reduced supply of natural sources of latex, wool, silk and other materials

• Emergence of synthetic polymers• Increased usage and development of nylons,

acrylics, neoprene, polyethylene

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Bakelite

• Developed in 1907 by Leo Baekeland • First synthetic polymer and first widely

manufactured plastic• At that time used to make everything from

telephones and radios to auto parts, furniture, and jewelry

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Polyethylene

• Simplest and most basic polymer chain• Made up of a long chain of Ethane molecules

(CH3-CH3)

• Monomer form is Ethylene (CH2=CH2)

• Available in Low Density and High Density Variations

• Commonly used for milk bottles, medicine bottles, bags, Toys

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PET

• Polyethylene Terephthalate• Derivative of polyethylene with terephthalate

molecule included in the chain• Durable and clear properties with oxygen and

water barrier• Great for soda bottles and drink containers

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Teflon

• PolyTetraFluoroEthylene• Discovered by Accident by Roy Plunkett at

Dupont in 1938 • Secret Weapon of WWII - used to coat bearings

and metal surfaces to reduce friction and wear and tear

• Now used for non stick pots and pans and dental floss

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Other Commonly Used Polymers

• Polypropylene (Microwavable Containers)• Polyvinylchloride (Water pipes)• Polystyrene (Foam Cups, Packing Peanuts)• Polycarbonate (aka Lexan, Bulletproof Glass)• Polyamide (Nylon)

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What Is Used to Make Plastic Stuff?

• Injection Molding• Injection Blow Molding• Injection Stretch Blow Molding• Extrusion Molding• Extrusion Blow Molding• Rotational Molding

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Why Use Plastic?

• Looks Good• Durable• Flexible• Light Weight• Easy to shape and color• Cheap

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The Plastic Age

• Stuff made out of plastic is everywhere• Cell phones, computer parts, car parts, tables,

chairs, etc.• New uses for plastic being discovered everyday• What used to be glass is now made in plastic• What used to be metal is now made in plastic• What used to be wood is now made in plastic• Plastic has revolutionized the world

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References

• http://web.umr.edu/~wlf/CHEM381/chap11.html

• http://www.calibre.co.nz/plastics.htm

• http://www.packagingtoday.com/intronaturalpolymers.htm

• http://www.packagingtoday.com/introplasticexplosion.htm

• http://www.teachingplastics.org/hands_on_plastics/intro_to_plastics/teachers.html